Some models of automotive vehicle seats are equipped with a pneumatic lumbar support system which includes provision of one or more inflatable air cells located in the lower region of the back rest and an electric air pump which, under the control of an operator switch, delivers low pressure air to the cell. Such systems enable an occupant of a seat to adjust the firmness or contour to meet his or her personal preference. Air cells may also be provided in other regions of the seat, such as the side bolster areas.
It is recognized that the cell, once inflated, must remain air-tight and not leak, since a change in air pressure within the cell would produce a corresponding objectionable change in the support provided to the occupant.
A source for air loss is the back flow of air from the cell through a non-reversible air pump, often the reciprocating piston type. One common valve used at the outlet of such pumps is a flapper-type valve which has sufficient sealing capability for the operation of a pump, but by its nature is not entirely leak proof and thus is unable to completely seal the air cell against air loss back through the pump. Consequently, it is common practice to install an external one-way check valve or solenoid valve in line between the outlet pump and the air cell to prevent such back flow through the pump. Such external valves, however, add to the cost and complexity of the system.
The present invention overcomes or greatly diminishes the foregoing objections.